1. Field of the Invention
The present invention relates to a liquid crystal display (LCD) device, and more particularly, to a multi-domain LCD device and a method for manufacturing the same.
2. Discussion of the Related Art
Ultra thin flat panel displays having a display screen with a thickness of several centimeters, especially LCD devices, are widely used in monitors for notebook computers, spacecraft, and aircraft.
Such an LCD device has low power consumption and is easy to carry. In this respect, the LCD device is receiving much attention as an advanced display device that can replace a cathode ray tube (CRT).
The LCD device includes a thin film transistor (TFT) substrate, a color filter substrate, and a liquid crystal layer sealed between the TFT substrate and the color filter substrate. The LCD is a non-light-emitting device that can obtain image effect based on electro-optical characteristic of the liquid crystal layer.
In other words, a TFT array and a pixel electrode are formed on the TFT substrate, while a black matrix pattern, a color filter layer, and a common electrode are formed on the color filter substrate. The TFT substrate and the color filter substrate are bonded to each other by a sealant such as epoxy resin.
A driving circuit is connected with the TFT substrate using a tape carrier package (TCP) as a medium. The driving circuit generates various control signals and signal voltages to display images.
Development of TFT-LCD applications have accelerated in accordance with increase of the dimensions and increase of the resolution. To increase the productivity and ensure the low cost, many efforts have continued in view of simplified process steps and improvement of yield. However, in spite of the trend toward large area, a problem arises in that contrast ratio depends on viewing angle. To solve this problem, various LCDs, such as a twist nematic LCD provided with a retardation film and a multi-domain LCD, have been proposed.
Recently, a liquid crystal display device which drives a liquid crystal by an auxiliary electrode electrically insulated from a pixel electrode without aligning the liquid crystal has been suggested. Such a related art liquid crystal display device will be described with reference to FIG. 1.
As shown in FIG. 1, the related art liquid crystal display device includes a first substrate, a second substrate, a plurality of data lines and gate lines, a TFT, a passivation film 37, a pixel electrode 13, and an auxiliary electrode 21. The data lines and gate lines are formed on the first substrate in first and second directions to divide the first substrate into a plurality of pixel regions. The TFT is formed in each pixel region on the first substrate and includes a gate electrode, a gate insulating film, a semiconductor layer, an ohmic contact layer, and source/drain electrodes. The passivation film 37 is formed on the first substrate. The pixel electrode 13 is formed on the passivation film 37 to be connected with the drain electrode. The auxiliary electrode 21 is formed on the gate insulating film to partially overlap the pixel electrode 13.
The related art liquid crystal display device further includes a light-shielding layer 25, a color filter layer 23 formed on the light-shielding layer 25, a common electrode 17 formed on the color filter layer 23, and a liquid crystal layer formed between the first substrate and the second substrate. The light-shielding layer 25 is formed on the second substrate to shield light leaked from the gate lines, the data lines, and the TFT.
The auxiliary electrode 21 formed around the pixel electrode 13 and an open region 27 of the common electrode 17 distort electric field applied to the liquid crystal layer so that liquid crystal molecules are variously driven within a unit pixel. This means that a dielectric energy of a distorted electric field places a liquid crystal director at a desired position when a voltage is applied to the LCD device.
However, the related art LCD device has several problems.
First, the open region should be formed in the common electrode to obtain multi-domain effect. To this end, the process for forming the open region in the common electrode is additionally required.
Furthermore, if the open region is not formed or has a small width, distortion range of the electric field required to define a plurality of domains is weak. Accordingly, there is a problem that the time when the liquid crystal director reaches a stable state is relatively longer. Such domains defined by the open region cause unstable texture for each domain, thereby deteriorating picture quality. Also, since high electric field is applied between the pixel electrode and the auxiliary electrode, luminance decreases and response time increases.